Balloon angioplasty is a widely used technique for treating vascular disease. In balloon angioplasty, a catheter having an inflatable balloon affixed to its distal end is guided through a patient's vasculature with the balloon in a deflated state, and the balloon is positioned within a vascular lesion. The balloon then is inflated to compress the atherosclerotic plaque against the vessel wall to restore adequate blood flow in the vessel.
It may be desirable to obtain various physiological measurements near the treatment site before, during or after an intravascular surgical procedure, such as balloon angioplasty. For example, it may be useful to obtain pressure or flow measurements near the site of a vascular occlusion. It may be beneficial to readily obtain such measurements at any time during the surgical procedure to assess the efficacy of the procedure.
One previously known method of placing a functional measurement wire at a treatment site is to exchange the functional measurement wire for the guide wire, i.e., to fully withdraw the guide wire from the vessel and then insert the functional measurement wire in place of the guide wire. Once the measurement is taken, the functional measurement wire is withdrawn and the guidewire reinserted. Such a method can be cumbersome and time-consuming, especially where it is desired to take multiple measurements during the course of a procedure.
Alternatively, a separate lumen may be provided in the catheter to accommodate the functional measurement wire, but this solution requires an increase in the catheter profile. Such an increase in profile, especially at the distal end of the catheter, may undesirably limit applicability of the device in smaller vessels, and also may result in an increase in the stiffness of the distal region of the catheter, thereby making it more difficult to negotiate tortuous anatomy.
Other alternative approaches are known in the art. For example, U.S. Pat. No. 5,921,957 to Killion et al. describes a balloon dilatation catheter having a guidewire lumen, and an atraumatic tip at the distal end of the catheter having an aperture that the guidewire passes through. The diameter of the aperture matches the diameter of the guidewire used in the procedure. The inner diameter of the guidewire lumen is described as substantially larger than the guidewire diameter used in the procedure, which creates a space between the guidewire and the guidewire lumen. In this available space, dye injections and pressure measurements may be performed via holes in the atraumatic tip that are disposed just proximal to the aperture. Accordingly, when the guidewire extends through the aperture, pressure measurements may be obtained via the extra space provided in the guidewire lumen and the holes in the atraumatic tip.
A main drawback associated with the device described in the Killion patent is that, in order to take pressure measurements through the guidewire lumen, the guidewire lumen must be relatively large to provide the additional lumen space that is required. By increasing the inner diameter of the guidewire lumen, the stiffness of the device is undesirably increased, and may render the device unsuitable for use in smaller vessels.
Still other previously-known devices have incorporated the use of a slit, port or frangible wall disposed in a lateral surface of the catheter that communicates with a guidewire lumen. For example, U.S. Pat. No. 5,921,971 to Agro et al. describes a catheter having a guidewire lumen extending along the catheter, wherein a slit in the catheter shaft allows a guidewire to be introduced into the guidewire lumen. The catheter further comprises two ancillary lumens that extend longitudinally along the length of the catheter.
One drawback associated with the device described in the Agro patent is that the guidewire may not be easily used in combination with other devices, such as a functional measurement wire, without removing the guidewire from the side slit and then introducing the measurement wire. Although the functional measurement wire alternatively may be introduced into one of the ancillary lumens, an increase in catheter profile occurs when providing a guidewire and functional measurement wire simultaneously at the distal end of the catheter.
In view of these disadvantages of previously known catheters, it would be desirable to provide a catheter that may be used in conjunction with a functional measurement wire to obtain measurements near a vascular treatment site.
It also would be desirable to provide a catheter that readily may introduce either a guidewire or a functional measurement wire to a vascular treatment site.
It further would be desirable to provide a catheter that readily may advance either a guidewire or a functional measurement wire to a vascular treatment site while maintaining a minimal distal catheter profile.